Method for the diagnosis of neuromyelitis optica

ABSTRACT

The present invention relates to a method for the diagnosis and/or risk stratification of neuromyelitis optica (abbreviated NMO), wherein a determination from a body sample of a patient/test subject is performed by means of artificial aquaporin-4 peptides. The invention further relates to a kit and to new artificial aquaporin-4 peptides as such.

RELATED APPLICATIONS

This application is a national stage application (under 35 U.S.C. §371) of PCT/EP2014/056383, filed Mar. 28, 2014, which claims benefit of European Application No. 13161822.5, filed Mar. 28, 2013.

SUBMISSION OF SEQUENCE LISTING

The Sequence Listing associated with this application is filed in electronic format via EFS-Web and hereby incorporated by reference into the specification in its entirety. The name of the text file containing the Sequence Listing is Sequence_Listing_074027_0033. The size of the text file is 7 KB, and the text file was created on Sep. 28, 2015.

FIELD OF THE INVENTION

The present invention relates to a method for the diagnosis and/or risk stratification of neuromyelitis optica (abbreviated NMO), wherein a determination from a body sample of a patient/test subject is performed with the aid of artificial aquaporin-4 peptides. The invention further relates to a kit and to new artificial aquaporin-4 peptides as such.

DESCRIPTION OF RELATED ART

Early diagnosis and differentiation of NMO, in particular for distinction from multiple sclerosis (MS), is necessary in order to provide suitable treatment for NMO.

In the prior art, human aquaporin-4 is described as an autoantigen for the detection and diagnosis of NMO (US 20080145870 and EP 1700120B1). In this connection, it is known that autoantibodies that specifically bind to human aquaporin-4 of the type depicted in SEQ ID No. 1 can be detected in the serum of NMO patients. A corresponding ELISA kit is available on the market (V. A. Lennon et al. A serum autoantibody marker of neuromyelitis optica: distinction from multiple sclerosis, Lancet 2004 364(9451): 2106-2112; V. A. Lennon et al. IgG marker of optic-spinal multiple sclerosis binds to the aquaporin-4 water channel, The Journal of Experimental Medicine 2005 202: 473-477 B; G. Weinshenker et al. Neuromyelitis optica IgG predicts relapse after longitudinally extensive transverse myelitits. Annals of Neurology 2006 59: 566-569).

Another disadvantage of the known diagnostic methods that use the previously known markers, however, is that early and complete detection of high-risk patients is inadequate and therefore risk stratification cannot be adequately performed. A problem addressed by the invention is therefore that of developing a method for the diagnosis and risk stratification of NMO that provides for an improved detection of high-risk patients, in particular in the point-of-care area.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 shows the structural differences between SEQ ID NO: 1 (human aquaporin-4) and SEQ ID NO: 2 according to the invention, containing GP spacers and the preferred subsequences,

FIG. 2a shows the diagnosis of NMO on the basis of 8 positive and 5 negative patient samples (hospital) by means of a Luminex bead assay using SEQ ID NO: 2, wherein, given an ascertained threshold value of 675 MFI (median fluorescence intensity), it was possible to correctly test 85% of the clinical patients,

FIG. 2b shows the stratification of NMO patients (“NMO”) versus multiple sclerosis patients (MS) and health patients (HV) by means of a Luminex bead assay using SEQ ID NO: 2,wherein 100% of the NMO patients were detected given an ascertained threshold value of 675 MFI.

FIG. 3 shows the diagnosis of NMO on the basis of 9 positive and 4 negative patient samples (hospital) by means of an ELISA assay according to the aforementioned example using SEQ ID NO: 2, Wherein it was possible to correctly test 92% of the clinical patients.

DETAILED DESCRIPTION OF THE INVENTION

It is disadvantageous in the prior art that sufficient sensitivity and/or specificity is usually not achieved with a rapid test in the point-of-care area.

The problem addressed by the present invention is therefore that of providing a method for the in vitro diagnosis and/or risk stratification of NMO.

The problem is solved by a method for the diagnosis and risk stratification of NMO, wherein a determination of autoantibodies from a body sample is performed with the aid of artificial aquaporin-4 peptides (the method according to the invention in the following).

Surprisingly, artificial aquaporin-4 peptides now exhibit high sensitivity and specificity for the diagnosis of NMO.

Within the scope of this invention, “aquaporin-4” is understood to mean a protein which participates in the regulation of the water and electrolyte balance primarily in the central nervous system, functioning as a water channel in cell membranes. These water channels are found particularly frequently in the sections that are classically affected by NMO. A suitable aquaporin-4 is depicted in SEQ ID No. 1 with 323 amino acids. Autoantibodies to the autoantigen aquaporin-4 are formed by peripheral plasma cells. After binding to their target antigen, said autoantibodies result in complement activation with local inflammatory demyelination and necrosis. The clinical picture corresponds to optic neuritis and local myelitis over three or more spinal segments with predominant localization at or in the vicinity of the blood-brain barrier.

The term “NMO” according to the invention (synonym: Devic's syndrome) relates to an inflammatory autoimmune disease of the central nervous system. This affects, in particular, the spinal marrow (myelitis) and the optic nerves (optic neuritis). The disease manifests as paralysis of the arms and legs, reduced sensation, and loss of bladder and bowel control, as well as blindness. Histologically, the affected tissue contains perivascular deposits of autoantibody immunoglobulins and complement factors. The autoantibodies that form are specific for NMO and can be used for the differential diagnosis of multiple sclerosis with the aid of the autoantigen human aquaporin-4.

Artificial aquaporin-4 peptides are used within the scope of the present invention, wherein, proceeding from SEQ ID No. 1, the artificial aquaporin-4 peptides additionally contain at least one spacer having 2 to 30 amino acids as compared to SEQ ID No. 1, preferably 2 to 20 amino acids, particularly preferably 2 to 10 amino acids, wherein the spacer does not contain any amino acid sequence of SEQ ID No. 1.

In a preferred embodiment of the invention, the spacer consists of hydrophilic amino acids (serine, threonine, etc.). In addition, helix-breaking amino acids are preferred, such as, in particular, proline (P) and glycine (G) (in the following: GP spacer).

In addition, the spacer can contain any amino acid as well as artificial amino acids.

Other suitable artificial aquaporin-4 peptides can be:

In another particular embodiment, at least one spacer is inserted/contained between amino acids 32 and 253 of SEQ ID No. 1. In addition, it is preferred that at least one spacer is inserted/contained in the regions of the transmembrane domains, selected from the sequence sections of amino acids 33 to 55, 70 to 92, 112 to 134, 154 to 176, 189 to 211 and 231 to 253 of SEQ ID No. 1.

In another preferred embodiment of the invention, proceeding from SEQ ID No. 1, amino acids can be omitted or deleted such that sequences can be obtained which at least contain the following subsequences selected from the group SDRPTARRWGKCGP (SEQ ID NO: 3), GGTEKPLPVD (SEQ ID NO: 4), CDSKRTD (SEQ ID NO: 5), NPARSFG (SEQ ID NO: 6), EFKRRFKEAFSKAA (SEQ ID NO: 7) or EFKRRFKEAFSKAAQQ (SEQ ID NO: 8) or EFKRRFKEAFSKAAQQTKG (SEQ ID NO: 9), DVDRGEEKKGKDQSGE (SEQ ID NO: 10) and comprise at least one spacer according to the invention.

The invention also relates to autoantigens for the diagnosis of NMO consisting of an amino acid sequence (polypeptide), wherein amino acids are omitted or deleted as compared to the SEQ ID No. 1, but at least the subsequences SDRPTARRWGKCGP (SEQ ID NO: 3), GGTEKPLPVD (SEQ ID NO: 4), CDSKRTD (SEQ ID NO: 5), NPARSFG (SEQ ID NO: 6), EFKRRFKEAFSKAA (SEQ ID NO: 7) and/or EFKRRFKEAFSKAAQQ (SEQ ID NO: 8) and/or EFKRRFKEAFSKAAQQTKG (SEQ ID NO: 9), DVDRGEEKKGKDQSGE (SEQ ID NO: 10) are contained and the polypeptide that is obtained consists of at most 250 amino acids, preferably at most 220 amino acids.

The invention also relates to autoantigens for the diagnosis of NMO consisting of an amino acid sequence (polypeptide), which contain the following subsequences selected from the group SDRPTARRWGKCGP (SEQ ID NO: 3), GGTEKPLPVD (SEQ ID NO: 4), CDSKRTD (SEQ ID NO: 5), NPARSFG (SEQ ID NO: 6), EFKRRFKEAFSKAA (SEQ ID NO: 7) and/or EFKRRFKEAFSKAAQQ (SEQ ID NO: 8) and/or EFKRRFKEAFSKAAQQTKG (SEQ ID NO: 9, DVDRGEEKKGKDQSGE (SEQ ID NO: 10) and comprise at least one spacer which contains 2 to 30 amino acids, preferably 2 to 20 amino acids, particularly preferably 2 to 10amino acids, and the polypeptide that is obtained consists of at most 250 amino acids, preferably at most 220 amino acids, wherein the spacer does not contain any amino acid sequence of SEQ ID No. 1.

A particularly preferred embodiment is SEQ ID No. 2, wherein a plurality of GP spacers are contained therein.

In addition, the invention relates to the use of these autoantigens according to the invention for the diagnosis of NMO according to one of the embodiments mentioned above or in the following.

A person skilled in the art is capable of producing corresponding amino acid sequences according to the invention, i.e. artificial aquaporin-4 peptides, e.g. fully synthetically by means of Merrifield synthesis (Weng C. Chan, Peter D. White: Fmoc Solid Phase Peptide Synthesis: A Practical Approach. Oxford University Press, Oxford/ New York 2000).

It is particularly preferred, however, to provide corresponding cDNA, e.g. proceeding from a cDNA, such as, e.g. SEQ ID No. 1 from EP1700120B1, wherein corresponding cDNA can be manufactured for the artificial aquaporin-4 peptides according to the invention. Corresponding techniques/specifications are found, e.g., in Sambrook et al, “Molecular Cloning, A laboratory handbook, 2nd edition (1989), CSH press, Cold Spring Harbor, N.Y.; Frederick M. Ausubel, Short protocols in molecular biology: a compendium of methods from current protocols in molecular biology, Volume 1, Wiley, 2002. Such a spacer based on DNA can be inserted into the cDNA by means of ligation, for example.

As mentioned above, the spacers are preferably inserted in the aforementioned regions of the transmembrane domains of SEQ ID No. 1. This results, according to the invention, in an increased sensitivity of autoantibodies of these artificial aquaporin-4 peptides that are obtained as compared to the known aquaporin-4, probably due to the omission of helices in the quaternary structure. This is also advantageous according to the invention, since a simplified genetic expression of the artificial aquaporin-4 peptides in a host, such as E. coli, is made possible.

Particularly advantageously, the method according to the invention provides for a reliable stratification in cases, in particular, of emergency and/or intensive care medicine. The method according to the invention therefore makes it possible to make clinical decisions that can result in rapid therapeutic success and can save lives. Such clinical decisions also comprise continued treatment with pharmaceuticals for handling or treating NMO.

Therefore, the invention also relates to a method for the diagnosis and/or risk stratification of NMO patients for the purpose of making clinical decisions, such as continued handling and treatment with pharmaceuticals, preferably in time-critical intensive care medicine or emergency medicine, including the decision to hospitalize the patient.

In another preferred embodiment, the method according to the invention therefore relates to the therapy control of NMO.

In another preferred embodiment of the method according to the invention, the diagnosis and/or risk stratification is carried out for purposes of prognosis, differential-diagnostic early detection and detection, assessing severity, and assessing the course of the disease in association with treatment.

In another preferred embodiment, the invention relates to a method for the in vitro diagnostics for the early diagnosis or differential diagnosis or prognosis of NMO, wherein a determination of autoantibodies from a body sample with the aid of artificial aquaporin-4 peptides is carried out on or by a patient to be examined.

In an embodiment of the method according to the invention, a body sample, in particular tissue or bodily fluid, preferably blood, either whole blood or serum or available plasma, is taken from the patient to be examined and the diagnosis is carried out in vitro/ex vivo, i.e. outside of the human or animal body. Due to the determination of autoantibodies from a body sample with the aid of artificial aquaporin-4 peptides, high sensitivity and specificity are obtained and the diagnosis or risk stratification can be carried out on the basis of the quantity available in at least one patient sample.

The quantity of autoantibodies can be determined, for example by means of radiolabeled or biotinylated artificial aquaporin-4 peptides (e.g. S(35) method or the like). Artificial aquaporin-4 peptides that remain free can be extracted, for example. In addition, autoantibodies bound to artificial aquaporin-4 peptides can be detected via fluorescence with the aid of anti-autoantibodies.

In another embodiment of the invention, the method according to the invention can be carried out within the framework of an in vitro diagnosis by means of parallel or simultaneous determinations with the aid of the artificial aquaporin-4 peptides (e.g., multititer plates having 96 or more cavities), wherein the determinations are carried out on at least one patient sample.

In another embodiment, the method according to the invention and its determinations can be carried out by means of a rapid test (e.g., lateral flow test or point-of-care), either as a single determination or a multiparameter determination. In a particularly preferred embodiment, this is a rapid test or a device that is suitable for use in emergency diagnostics.

Another problem is that of providing a corresponding diagnostic device or its use for carrying out the method according to the invention.

Within the scope of this invention, such a diagnostic device is understood to be, in particular, an array or an assay (e.g., immunoassay, ELISA, etc.), in the broadest sense a device for carrying out the method according to the invention.

The detection and the quantification of bound autoimmune antibodies on the artificial aquaporin-4 peptides according to the invention can also be carried out with the aid of other protein diagnostic methods commonly known to a person skilled in the art, in particular using radiolabled or enzyme- or fluorescence-labeled antibodies. Examples include, in particular, bioanalytical methods which are suitable therefor, such as, for example immunohistochemistry, antibody arrays, Luminex, ELISA, immunofluorescence, radioimmunoassays, and other suitable bioanalytical methods, such as for example mass-spectrometric methods, e.g. MRM (multi-reaction monitoring) or AQUA (absolute quantification), with the aid of which the autoimmune antibodies are quantitatively measured and the particular detection can be carried out.

The invention also relates to a kit for the diagnosis and/or risk stratification of NMO, containing artificial aquaporin-4 peptides including detection reagents and, optionally, auxiliary agents. Such detection reagents comprise, e.g. antibodies, beads, etc.

The following examples and figures are provided to explain the invention in greater detail, although the invention is not limited to these examples and figures.

FIG. 1 shows the structural differences between SEQ ID No. 1 (human aquaporin-4) and SEQ ID No. 2 according to the invention, containing GP spacers and the preferred subsequences.

EXAMPLES

The method according to the invention can be carried out, e.g. in a manner analogous to Lennon 2004, 2005 (supra).

Calibrators, some of which are positive controls and some of which are negative controls, are dispensed in a microtiter plate (96 wells and more).

An artificial aquaporin-4 according to SEQ ID No. 2, according to the invention, is used as the autoantigen, e.g. biotinylated or radiolabeled and dissolved in buffer (e.g. PBS), and is stirred.

In the case of biotinylated artificial aquaporin-4 according to SEQ ID No. 2, an autoantibody binding detection can take place by means of streptavidin peroxidase (see, e.g. Prescott, L. M.; Harley, J. P.; Klein, D. A.: Microbiology. 5th Edition. McGraw Hill, Boston 2002).

50 μl NMO patient serum are added in a microtiter plate, each with controls and calibrators.

25 μl of a solution of biotinylated artificial aquaporin-4 according to SEQ ID No. 2 are added to each well.

The ELISA prepared in this manner is washed three times with a washing solution. Next, 100 μl streptavidin peroxidase is added to the wells and the wells are shaken and washed, then a peroxidase substrate is added to the wells and the wells are incubated. A photometric evaluation is then carried out by reference to a calibration curve.

The method according to the invention can also be carried out using a common radioimmunoassay (RIA).

FIG. 2a shows the diagnosis of NMO on the basis of 8 positive and 5 negative patient samples (hospital) by means of a Luminex bead assay using SEQ ID No. 2, wherein, given an ascertained threshold value of 675 MFI (median fluorescence intensity), it was possible to correctly test 85% of the clinical patients.

FIG. 2b shows the stratification of NMO patients (“NMO”) versus multiple sclerosis patients (MS) and healthy patients (HV) by means of a Luminex bead assay using SEQ ID No. 2, wherein 100% of the NMO patients were detected given an asertained threshold value of 675 MFI.

FIG. 3 shows the diagnosis of NMO on the basis of 9 positive and 4 negative patient samples (hospital) by means of an ELISA assay according to the aforementioned example using SEQ ID NO. 2, wherein it was possible to correctly test 92% of the clinical patients. 

The invention claimed is:
 1. An autoantigen consisting of the amino acid sequence of SEQ ID NO:
 2. 2. Autoantigens for in vitro diagnosis of neuromyelitis optica consisting of an amino acid sequence, which contain the following sequences selected from the group SDRPTARRWGKCGP (SEQ ID NO: 3), GGTEKPLPVD (SEQ ID NO: 4), CDSKRTD (SEQ ID NO: 5), NPARSFG (SEQ ID NO: 6), EFKRRFKEAFSKAA (SEQ ID NO: 7) or EFKRRFKEAFSKAAQQ (SEQ ID NO: 8) or EFKRRFKEAFSKAAQQTKG (SEQ ID NO: 9), DVDRGEEKKGKDQSGE (SEQ ID NO: 10) and comprise at least one spacer which contains 2 to 30 amino acids, 2 to 20 amino acids, or 2 to 10 amino acids, and the polypeptide that is obtained consists of at most 250 amino acids, wherein the spacer does not contain any amino acid sequence of SEQ ID NO:
 1. 3. A kit for in vitro diagnosis of neuromyelitis optica, containing artificial aquaporin-4 peptides, detection reagents and auxiliary agents, wherein said artificial aquaporin-4 peptides contain the following sequences selected from the group SDRPTARRWGKCGP (SEQ ID NO: 3), GGTEKPLPVD (SEQ ID NO: 4), CDSKRTD (SEQ ID NO: 5), NPARSFG (SEQ ID NO: 6), EFKRRFKEAFSKAA (SEQ ID NO: 7) or EFKRRFKEAFSKAAQQ (SEQ ID NO: 8) or EFKRRFKEAFSKAAQQTKG (SEQ ID NO: 9), DVDRGEEKKGKDQSGE (SEQ ID NO: 10) and comprise at least one spacer which contains 2 to 30 amino acids, 2 to 20 amino acids, or 2 to 10 amino acids, and the polypeptide that is obtained consists of at most 250 amino acids, wherein the spacer does not contain any amino acid sequence of SEQ ID NO: 1, or the amino acid sequence of SEQ ID NO:
 2. 